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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1052 (Engine Controls And Fuel - 4.3L - DTC P0340 To DTC P2138) >> DTC P0641 or P0651 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Sierra and 2008 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT: Additional DTCs may set when disconnecting components.
  1. Ignition OFF, disconnect the harness connector of all the sensors connected to the 5-volt reference bus for the applicable DTC. Refer to Circuit/System Description above.
    2. IMPORTANT: A short to voltage on the signal circuit of certain components may cause this DTC to set.
  2. Ignition ON, test for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.
    • If less than the specified range, test all of the 5-volt reference circuits for a short to ground. If all circuits test normal, replace the ECM.
    • If greater than the specified range, test for a short to voltage on all of the 5-volt reference circuits, or the signal circuit for each component associated with the appropriate 5-volt reference bus for a short to voltage. If all circuits test normal, replace the ECM.
  3. Connect each component associated with the appropriate 5-volt reference bus, one at a time, while monitoring the voltage. The voltage should not change more than 1 volt.
    • If the voltage display changes more than the specified range when a component is connected, replace the component.
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